diff --git a/CGAL_Core/include/CGAL/CORE/ExprRep.h b/CGAL_Core/include/CGAL/CORE/ExprRep.h
index 5e5b819fce1..557086fa8f1 100644
--- a/CGAL_Core/include/CGAL/CORE/ExprRep.h
+++ b/CGAL_Core/include/CGAL/CORE/ExprRep.h
@@ -922,7 +922,7 @@ protected:
     return Operator::get_name();
   }
 private:
-  static Operator Op;
+  Operator Op;
 };//AddSubRep class
 
 template <class Operator>